CODEWITHSUNDEEP
stringpowershellpattern-matchingconditional-statements
Igor Shvets
Igor Shvets

Reputation: 1

Searching for specific string in a file

I need to find this pattern, "LogEntry=", across multiple lines in the following file: C:\test.conf

And change the line to read: "LogEntry=&MAC=" instead.

The script works fine so far to do that, but if someone runs the script twice it will re-add the same pattern, doubling it up.

I need to find a way to put a check in place to know if the file already has that pattern in it. Could someone please give me a hand with this one ?

Upvotes: 0

Views: 114

Answers (1)

Keith Hill
Keith Hill

Reputation: 201662

Use negative lookahead in your regex e.g.:

'LogEntry=(?!&MAC=)'

That regex will not match the already modified line. Read more about look ahead/behind zero length assertions.

BTW if you have the PowerShell Community Extensions, you can do this edit operatio with a single command:

Edit-File C:\test.conf -Pattern 'LogEntry=(?!&MAC=)' -Replace 'LogEntry=&MAC='

And if you can't use PSCX's Edit-File, here is roughly the equivalent:

$content = Get-Content C:\test.temp
$content | Foreach {$_ -replace 'LogEntry=(?!&MAC=)','LogEntry=&MAC='} | Out-File -Encoding ASCII

I don't know what the file encoding is for your file. You need to know that and use the appropriate encoding on the Out-File command. If you don't specify the encoding, it defaults to Unicode.

Upvotes: 1

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